The present invention relates to vehicle electrical systems, and more particularly, to a system for automatically disconnecting radios and other auxiliary equipment in cars and trucks from their batteries to prevent the same from going dead when they are left unattended for long periods of time.
Many vehicles, particularly police cars, emergency vans, wrecking trucks and fire engines, contain auxiliary equipment including two-way radios and public address systems. These are normally not switched on and off by the vehicle ignition so that they can be used when the vehicle ignition has been turned off. It often goes unnoticed that such auxiliary equipment has been left on at the end of the day when the vehicle is parked and the operator goes off duty. A public address system on a vehicle may be quietly idling. If there is nothing happening at a dispatch desk, a two-way radio may be silent. The same is true of a cellular telephone. Even if the operator remembers to switch off the radio, he or she may forget to shut off another piece of auxiliary equipment. All the auxiliary equipment can be tied to the battery through a manual master switch, but again, the operator has to remember to turn it off. Because of the foregoing, it is not uncommon for an operator to find that the battery of his or her vehicle has been completely drained of power when he or she returns after a weekend. The vehicle must then receive a jump start before it can be used.
It would be desirable to automatically disconnect such equipment from the battery. However, such disconnection should only occur when the equipment is not being used, and not likely to be used. Frequently policemen monitor their two-way radios when outside their parked vehicles, e.g. at the scene of a crime. Furthermore, any automatic disconnection should not be permanent, but instead should include automatic reconnection so that the operator can simply turn on the vehicle ignition and thereafter use all the auxiliary equipment in normal fashion.